MIT patrol officer Sean Collier, a Somerville resident, gave his life in the line of duty, shot by the bombing suspects as they fled from justice.

By Harry Kane

Last week’s marathon bombing in Boston on Patriots’ Day left three dead and scores of sidelined spectators wounded. What proceeded next was a manhunt for the two suspects caught on video surveillance – a 26 year old wearing a black hat and a 19 year old wearing a white hat – both carrying backpacks, allegedly with pressure-cooker homemade bombs.

At 2:50 p.m. on Monday, April 15, 2013, the first of two bombs exploded beside the Boston Marathon finish line on Beacon Street. Moments later, a second bomb detonated on the same side of the street, only a stone’s throw away. According to reports, some 170 people were injured in the blasts, almost 20 of which were critically injured.

Plumes of smoke from the explosions created a haze of confusion while emergency workers carried bloodied spectators to safety across shattered glass from storefront windows. Screams of terror from disoriented runners and onlookers echoed the fears of panic stricken Bostonians.

Shortly after the blasts on Beacon Street, in an apparent unrelated event, the John F. Kennedy Library’s mechanical room had a fire, but nobody was injured.

Cheryl Fiandaca, bureau chief of public information at the Boston Police Department, tweeted at 5:46 p.m. on April 15 that the FBI had “taken over the investigation.” Federal, state and local Law Enforcement evacuated Copley Square and began the search for other devices, going over the crime scene with a fine toothcomb, looking for any more bombs that may have been left in trashcans along the race route.

Victims were taken to various hospitals for surgery. Some had sustained “complex lower extremity trauma,” according to Peter J. Fagenholz, a trauma surgeon on duty at Massachusetts General Hospital, who answered questions during the press conference.

President Barack Obama addressed the nation from the White House shortly after 6 p.m. “We will get to the bottom of this…any responsible individuals, any groups will feel the full weight of justice.”

And then, the search was on for the “persons of interest” who were responsible for the act of terrorism. While the whole country waited, the joint terrorism task force scoured metro Boston for any leads.

The media released the identities of the three individuals who lost their lives in the bombing: Martin Richard, 8, Lu Lingzi, 23, and Krystle Campbell, 29.

Several days would pass before the surveillance video was released in an effort to find the persons of interest. During a press conference on April 18 at approximately 5:20 p.m. the FBI released pictures and video of suspect one and suspect two. It wouldn’t take long before the Marathon bombers were identified, and a massive manhunt was underway.

At 10:20 p.m. on Thursday night, reports of a robbery at a 7-11 on Massachusetts Avenue tipped off police to the suspects’ whereabouts. While it is unclear whether the two Marathon bombers had anything to do with the robbery, they were identified as 26-year-old Tamerlan Tsarnaev, and 19-year-old Dzhokhar A. Tsarnaev. They were brothers.

One theory from renowned criminologist James Allen Fox of Northeastern University proposed that the Chechnyan brothers had been radicalized by Islamic anti-American ideologies on terrorist sponsored websites. “There are so many anti-American websites that one could gravitate to,” said Fox, on the Fox News Network.

Shortly after the robbery, MIT patrol officer Sean Collier, 26, of Somerville, was shot and killed in the line of duty. “He was assassinated in his cruiser,” said Boston Police Commissioner Ed Davis. Collier had worked for the MIT police since Jan. 2012.

Learning of Collier’s death, Somerville Mayor Joseph A. Curtatone issued the following statement: “Our hearts are broken today, as we learn about the death of one of our own, Sean Collier. Sean had been a dedicated civilian employee in the Somerville Police Department, working to become a Somerville Police Officer. Sean was a tremendous young man, and we grieve for his family and friends in Somerville, and in our Department. Similarly, we grieve for the families and friends of all victims of this week’s acts of senseless violence, and hope that we can continue to unite in support of all affected.”

Alderman Bob Trane commented to The Somerville News on the passing of Sean Collier: “I learned of Sean’s passing during the night and I am still in shock by this devastating news. I have never met a young man so dedicated to a career in law enforcement. He showed a maturity well beyond his years. It was obvious to me from the moment I met him that he was a special person. He so wanted to help people and serve his community. This is a tragic loss for all that knew him, my thoughts and prayers are with his family and friends.”

Following the cold blooded murder of Collier, the two brothers carjacked a Mercedes SUV at gunpoint on 3rd Street in Cambridge, taking a hostage, but later releasing him unharmed. The pursuit went into a residential neighborhood and 90 minutes later the car was spotted in Watertown.

A shootout between police and the suspects ensued, leaving the older brother riddled with bullets. The younger brother, Dzhokhar, escaped the shootout in the car and allegedly drove over his brother’s body as he fled the scene. Dzhokhar later ditched the car and ran away on foot.

Another officer had been critically wounded during the shootout in Watertown. MBTA Transit Police Officer Richard H. Donohue, 33, who had been on the force for 3 years and had attended the same academy as Collier was rushed to the hospital.

Following a violent night of gunfire, much of metro Boston went on lock down.

A door-to-door dragnet within a 20-block perimeter of the shootout in Watertown brought law enforcement officials from all areas to canvas the area in search of the suspect. Authorities searched every “nook and cranny” but were unable to turn up any “fruitful” leads.

At approximately 6:05 p.m. Gov. Deval Patrick lifted a stay-in-door request. But less than an hour later, David Henneberry, resident of 67 Franklin St. in Watertown, discovered blood and a tear in the tarp of his boat parked in the backyard. The suspect had been hiding in the bow of the 22-foot Seahawk cruiser, only two blocks outside the 20-block perimeter. Henneberry called the police. The police arrived and exchanged gunfire with the suspect in the boat.

At nightfall, the FBI tactical command team took over and surrounded the boat. They used flash bang grenades to stun and disorient the suspect before capturing him. Dzhokhar A. Tsarnaev was taken into custody at 8:44 p.m. on April 19.